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Assoc. w/ Trochlear n. (CN4)
Location:
in the central grey matter of midbrain, ventral to cerebral aqueduct and close to midline at the level of inf. colliculi.
Caudal to the oculomotor nuc. and its ventral aspect is closely related to MLF.
Target: Superior oblique
Fibres course
from each trochlear nucleus course dorsally and then medially around the central grey matter to reach the cranial end of superior medullary velum, wherein they decussate to emerge on the lateral side of frenulum veli on the dorsal aspect of the midbrain.
The trochlear nerve fibres have an unusual course and this is the only nerve which emerges from the dorsal aspect of brainstem.
It has been suggested that this nerve originally supplied the muscles of pineal eye, which would account for its dorsal course.Unique features of the trochlear nerve
It is the smallest and most slender cranial nerve.
It decussates before emerging from the brain.
It emerges on the dorsal aspect of the brain.
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